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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/24—Acids; Salts thereof
  • C08K3/26—Carbonates; Bicarbonates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
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  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/13—Phenols; Phenolates
  • C08K5/134—Phenols containing ester groups
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
  • C08K5/3412—Heterocyclic compounds having nitrogen in the ring having one nitrogen atom in the ring
  • C08K5/3432—Six-membered rings
  • C08K5/3435—Piperidines
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  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/544—Silicon-containing compounds containing nitrogen
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  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
  • C09D183/04—Polysiloxanes
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  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J183/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Adhesives based on derivatives of such polymers
  • C09J183/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/18—Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/24—Acids; Salts thereof
  • C08K3/26—Carbonates; Bicarbonates
  • C08K2003/265—Calcium, strontium or barium carbonate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/006—Additives being defined by their surface area
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/019—Specific properties of additives the composition being defined by the absence of a certain additive
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2312/00—Crosslinking
  • C08L2312/08—Crosslinking by silane

Definitions

• the invention relates to a one-component moisture-curable silicone composition, to a method for bonding or joining with the composition, and to the use thereof.
• RTV room-temperature vulcanizing
• One- and two-component RTV silicones are also referred to respectively as RTV-1 silicones and RTV-2 silicones.
• RTV-1 silicones have long been known. It is likewise known that formulations of this kind can be cured on the basis of so-called neutral crosslinking. Neutral crosslinking systems classically release oxime compounds, which have an odor that is perceived as very unpleasant and are harmful to health. RTV-1 silicones can alternatively be formulated with crosslinkers containing alkoxy groups. The crosslinking elimination products are then alcohols, which have a considerably less unpleasant odor.
• the crosslinkers used generally comprise oligomeric functional silicones, as well as monomeric or oligomeric silanes with alkoxy functional groups.
• silicones show superior resistance against degradation, for example caused by oxidative stress, UV irradiation, or thermal influence. This is the reason why silicones, unlike polyurethanes or compositions based on silane-terminated organic polymers, hardly ever are compounded using UV- or oxidation stabilizers, since the polydiorganosiloxane chain of silicone polymers is very resistant against chemical or physical degradation.
• silicone compositions for applications where environmental durability is a critical requirement, such as for construction and fenestration applications where weathering from constant exposures to variations in external temperature, humidity, and UV light are present.
• RTV-1 silicones however, like all one-component reactive compositions, intrinsically have issues with storage stability. Since all reactive ingredients are stored within one container, only lacking water to cure, there are commonly issues with silicones starting to cure over time within their package, since many ingredients such as fillers commonly contain trace amounts of water even when dried carefully. One other source of the moisture is coming from the moisture ingression from external environment. Overtime, especially under elevated temperature conditions, RTV-1 silicone formulations containing fillers often gradually increase in viscosity due to initiation of crosslinking reactions caused by trace amounts of water. While it is possible to mitigate these effects by addition of drying agents such as highly reactive organosilanes or molecular sieves, these reactions can hardly be fully suppressed, which limits the shelf life of RTV-1 silicones in general. Furthermore, addition of large amounts of silane or solid drying agents influences the mechanical properties of the cured silicone composition, which restricts this solution in some applications.
• RTV-1 silicones often have are their relatively low pumpability, as they intrinsically possess a relatively high viscosity and limited shear-thinning properties. This is an issue that has become more relevant recently, as many application processes such as assembly operations in industry increasingly rely on automatic application involving pumping of the adhesive compositions. Pumpability of RTV-1 compositions can be improved by adding low viscous plasticizers or extenders to the formulation, or by reducing the content of solid ingredients such as fillers. However, this again severely influences the final mechanical properties of the cured material and reduces, for example, mechanical strength or toughness. Especially in industrial assembly operations, however, excellent mechanical properties are of key importance in the silicone adhesive, and thus such formulation adaptations are often not viable.
• the present invention relates to one-component moisture-curable silicone composition
• a moisture-curable silicone composition comprising
• polymer in the present document firstly encompasses a collective of macromolecules that are chemically uniform but differ in relation to degree of polymerization, molar mass, and chain length, said collective having been prepared by a "poly" reaction (polymerization, polyaddition, polycondensation).
• the term secondly also encompasses derivatives of such a collective of macromolecules from "poly" reactions, i.e. compounds that have been obtained by reactions, for example additions or substitutions, of functional groups on defined macromolecules and that may be chemically uniform or chemically nonuniform.
• prepolymers too, i.e. reactive oligomeric initial adducts, the functional groups of which are involved in the formation of macromolecules.
• Molecular weight refers to the molar mass (in g/mol) of a molecule or a molecule residue.
• Average molecular weight refers to the number-average molecular weight (M n ) of an oligomeric or polymeric mixture of molecules or molecule residues. It is typically determined by gel-permeation chromatography (GPC) against polydimethylsiloxane as standard.
• viscosity refers to the dynamic viscosity or shear viscosity, which is defined by the ratio between the shear stress and the shear rate (speed gradient) and is determined as described in DIN EN ISO 3219. The measurement can be carried out at 25°C using an MCR101 cone-plate viscometer from Anton Paar, Austria, with a type CP 25-1 cone. Unless otherwise stated, the reported viscosity values relate to a shear rate of 0.5 s -1 .
• a substance or composition is referred to as “storage-stable” or “storable” when it can be stored at room temperature in a suitable container over a prolonged period, typically over at least 3 months up to 6 months or more, without this storage resulting in any change in its application or use properties to an extent relevant to its use.
• mass and “weight” are used synonymously in this document.
• a “percentage by weight” refers to a percentage mass fraction that, unless otherwise stated, relates to the mass (the weight) of the total composition or, depending on the context, of the entire molecule.
• Root temperature refers to a temperature of 23°C.
• a silane is a silicon compound that consists of a silicon atom and 4 functional groups or atoms attached to it.
• a siloxane is a compound that includes at least two silicon atoms bridged by an oxygen atom. Siloxanes are thus condensation products of silanes.
• An organosilane is a monomeric silicon compound having at least one non-hydrolyzable group that is linked via a Si-C bond.
• An organosiloxane is a compound obtainable from the condensation of at least two organosilanes.
• An alkoxysilane is a monomeric silane having at least one alkoxy group attached to the Si atom.
• a trialkoxysilane and a tetraalkoxysilane are a monomeric silane having respectively three and four alkoxy groups that are attached to the Si atom.
• the alkoxy group can be, for example, a C 1 -C 8 alkoxy group.
• An alkoxysiloxane is a compound obtainable from the condensation of at least two alkoxysilanes, but still has at least one alkoxy group after the condensation.
• An organoalkoxysilane is a monomeric silane having at least one alkoxy group and at least one non-hydrolyzable group that is linked via a Si-C bond.
• An organoalkoxysiloxane is a compound obtainable from the condensation of at least two organoalkoxysilanes or at least one alkoxysilane and an organoalkoxysilane, but still has at least one alkoxy group after the condensation.
• the one-component moisture-curable silicone composition is in particular an RTV-1 silicone.
• RTV-1 silicones cure at room temperature through contact with water, generally through contact with atmospheric humidity in the air.
• the one-component moisture-curable silicone composition comprises firstly one or more crosslinkable polydiorganosiloxanes P having alkoxysilane end groups.
• crosslinkable polydiorganosiloxanes are well known to the person skilled in the art.
• the crosslinkable polydiorganosiloxanes initially have alkoxy groups attached to silicon, which can hydrolyze to silanol groups under influence of moisture, through which crosslinking is possible. These alkoxysilane groups are located at the end of the polydiorganosioxane chain.
• Such polydiorganosiloxanes having terminal silanol groups are also referred to as ⁇ , ⁇ -functional polydiorganosiloxanes.
• the alkoxy groups on the polydiorganosiloxanes P, or, after hydrolysis the silanol groups formed therefrom, can react with the alkoxy groups or, after hydrolysis the silanol groups formed therefrom, of the crosslinker V, or other polydiorganosiloxanes P in the composition to form a bond.
• This bond is formed in a condensation reaction. This generally results in the release of byproducts such as water and/or alcohol. It is possible and even probable that an alkoxysilane may first hydrolyze to a silanol before the condensation takes place. These reactions take place preferentially and much more efficiently under the influence of a condensation catalyst K, as it is also contained in the composition of the invention. This is described further below.
• the viscosity of the polydiorganosiloxanes P may vary within wide ranges depending on the intended use.
• the polydiorganylsiloxane P used in accordance with the invention can, for example, have a viscosity of 10 to 500'000 mPa s, preferably 5'000 to 400'000 mPa s, and particularly preferably 10'000 to 320'000 mPa s, at a temperature of 23°C.
• the polydiorganosiloxane P is preferably a linear polydiorganosiloxane of the formula (I),
• the radicals R 1 and R 2 are preferably independently selected from alkyl groups having 1 to 5, in particular 1 to 3, carbon atoms, such as propyl, ethyl, and methyl, methyl being particularly preferred, wherein some of the alkyl groups, in particular methyl, may be optionally replaced by other groups such as vinyl, phenyl, or 3,3,3-trifluoropropyl.
• the radical R 3 if present, is preferably independently selected from phenyl, vinyl or methyl groups.
• radicals R 1 , R 2 , and R 3 in formula (I) are particularly preferably methyl groups.
• radicals R 4 are methoxy groups.
• the index m in formula (I) is chosen such that the polydiorganosiloxane has the viscosity indicated above.
• the index m in the formula (I) may, for example, be in the range from 10 to 5'000 and preferably 100 to 1'500.
• Suitable polydiorganosiloxanes as shown in formula (I) are known and commercially available.
• the preparation of such polydiorganosiloxanes is also carried out in a known manner, as described, for example, in EP0658588 .
• the composition comprises between 40 wt.-% and 70 wt.-%, preferably between 50 wt.-% and 60 wt.-%, of said crosslinkable polydiorganosiloxane P, based on the total composition.
• composition of the invention further comprises at least condensation catalyst K. These are used for catalysis of the condensation/crosslinking that takes place between the crosslinkable polydiorganosiloxanes P and the crosslinker V (and further silane-functional constituents, if present) in the presence of moisture/water, and/or for catalysis of the preceding hydrolysis to silanols in the case of alkoxysilane groups.
• the condensation catalyst K can be any conventional catalyst used for these RTV silicone systems, preferably a metal catalyst.
• Metal catalysts can in particular be compounds or complexes of elements of groups 1, 2, 4, 12, 14 or 15 of the periodic table of elements, preferably groups 4 or 14.
• the condensation catalyst K is preferably an organotin compound or a titanate or a zirconate or a bismuthate or an aluminate.
• the condensation catalyst is particularly preferably an organotin compound.
• condensation catalysts K are commercially available. It is also possible and in certain cases even preferred to use mixtures of different catalysts as condensation catalyst K.
• Suitable titanates are commercially available, for example, under the trade names Tyzoh ® AA-105, PITA, TnBT, TPT, TOT, IAM, IBAY from Dorf Ketal, India.
• Suitable zirconates are commercially available, for example, under the trade names Tyzoh ® NBZ, NPZ, TEAZ, 212, 215, 217, 223 from Dorf Ketal or under the trade names K-Kat ® 4205 or K-Kat ® XC-6212 from King Industries.
• Suitable bismuthates are commercially available for example under the brand names Borchi ® Kat (Borchers GmbH) or Tegokat ® (Goldschmidt TIB GmbH), Neobi ® 200, Shepherd, Coscat ® , Caschem.
• a suitable aluminate is available, for example, under the trade name K-Kat ® 5218 from King Industries.
• Amidines and guanidines are also suitable as condensation catalysts K.
• the condensation catalyst K is in particular an organotin compound.
• organotin compounds are dialkyltin compounds, selected for example from dimethyltin di-2-ethylhexanoate, dimethyltin dilaurate, di-n-butyltin diacetate, di-n-butyltin di-2-ethylhexanoate, di-n-butyltin dicaprylate, din-butyltin di-2,2-dimethyloctanoate, di-n-butyltin dilaurate, di-n-butyltin distearate, di-n-butyltin dimaleate, di-n-butyltin dioleate, di-n-octyltin di-2-ethylhexanoate, di-n-octyltin di-2,2-dimethyloctanoate, di-n-octyltin dimaleate, di-n-
• composition of the invention further comprises at least one organoalkoxysilane or organoalkoxysiloxane crosslinker V that has alkoxysilane groups, preferably between 2 and 3 alkoxysilane groups.
• crosslinker V should have at least one silane group that has at least 2 alkoxy substituents.
• the crosslinker V has at least 2 alkoxysilane groups, preferably at least 3 or more (only in the case of a siloxane, i.e. of an oligomeric silane).
• Suitable alkoxy groups are in particular methoxy, ethoxy, butoxy, and propoxy groups. Preference is given to methoxy and ethoxy groups.
• crosslinker V preferably has 1, 2 or more (only in the case of oligomeric siloxanes) non-hydrolyzable functional groups, in particular alkyl groups or alkenyl groups or aryl groups, which all may contain heteroatoms.
• the non-hydrolyzable functional groups are preferably selected from methyl, ethyl, vinyl, n-propyl, cyclopentyl, phenyl, cyclohexyl, n-octyl, isooctyl, and hexadecyl.
• the non-hydrolyzable functional groups are preferably phenyl groups.
• crosslinker V in particular tetraethoxysilane and tetra-n-propoxysilane.
• non-hydrolyzable functional groups may also contain heteroatoms, in particular selected from O, N, S, and Si.
• heteroatoms in particular selected from O, N, S, and Si.
• groups containing heteroatoms are aminoalkyl groups, (meth)acryloxyalkyl groups, glycidoxyalkyl groups, and thioalkyl groups.
• monomeric organoalkoxysilane crosslinkers V are methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, isooctyltrimethoxysilane, methylvinyldimethoxysilane or the corresponding compounds in which the methoxy group is replaced by ethoxy or propoxy, such as methyltriethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, methyltripropoxysilane, and phenyltripropoxysilane.
• the oligomeric organoalkoxysiloxane crosslinkers V are condensation products of one or more such monomeric silane crosslinkers, optionally with the use of further silanes such as tetraalkoxysilanes. Oligomeric siloxanes of this kind are known and are commercially available, for example under the Dynasylan ® 6490 trade names from Evonik Degussa GmbH.
• Oligomers of functional silanes are three-dimensional compounds with complex structures made up of tetrahedral silane/siloxane units.
• the oligomeric siloxane may be formed, for example, from hydrolysis and condensation of one or more identical or different monomeric silanes.
• a siloxane containing alkoxy groups may be linear, cyclic or three-dimensionally branched. It is preferably a siloxane containing oligomeric alkoxy groups.
• An oligomeric siloxane of this kind contains functional groups that originate from the monomeric silanes used for the synthesis thereof. For example, an initial condensation of two tetramethoxysilane molecules results in a dimer containing six functional groups, with one functional group in each molecule forming the linkage through condensation. As already set out, the structure of the oligomers formed may be complex. The number of functional groups in the oligomer can vary according to the degree of condensation, nature of condensation, and monomeric silanes used, but is at least 2, but generally greater, for example 4 or more.
• the degree of condensation of the oligomeric siloxane i.e. the number of monomeric silanes condensed with one another, may vary within wide ranges according to the end use, but may, for example, be within the range from 2 to 200 and preferably from 4 to 50. It will be apparent that the degree of condensation, especially in the case of higher degrees of condensation, is frequently only an average.
• the degree of condensation relates to the number of monomeric alkoxysilanes in the siloxane that are condensed with one another and can also be referred to as the degree of polymerization.
• the average degree of condensation of a siloxane containing alkoxy groups is at least 5, preferably at least 6, and more preferably at least 7.
• the average degree of condensation of the siloxane containing alkoxy groups may vary within wide ranges according to the end use and may preferably be, for example, not more than 15 and more preferably not more than 12. It will be apparent that the degree of condensation, especially in the case of higher degrees of condensation, is often an average, i.e. the siloxane is generally a mixture of compounds of varying degrees of condensation.
• the average degree of condensation here means the average degree of condensation based on the number average. As is known to the person skilled in the art, this can be determined by measuring the siloxane by 29 Si NMR spectroscopy and evaluating the spectrum obtained. The measurement and determination can be carried out according to the details provided by J. Zhang et al, J Sol-Gel Sci Technol, 2010, 56, 197-202 .
• crosslinker V comprises at least one organoalkoxysilane or organoalkoxysiloxane that contains at least one aminoalkyl group having a primary and/or secondary amino group.
• Monomeric such organoalkoxysilanes may contain 1 or 2 aminoalkyl groups and 2 or 3 alkoxy groups per silicon atom; oligomeric such organoalkoxysiloxanes may also have more or fewer amino groups.
• organoalkoxysilane or organoalkoxysiloxane having aminoalkyl groups results not only in the composition curing more rapidly as a consequence of the amino group having a co-catalytic effect, but also improves adhesion on many substrates.
• monomeric organoalkoxysilanes having aminoalkyl groups as crosslinker V are 3-aminopropyltrimethoxysilane and 2-aminoethyl-3-aminopropyltrimethoxysilane and the corresponding compounds in which the methoxy group is replaced by ethoxy or propoxy, such as 3-aminopropyltriethoxysilane.
• Further examples are bis(trimethoxysilylpropyl)amine and N-(n-butyl)-3-aminopropyltrimethoxysilane, and also their analogs having ethoxysilane groups instead of methoxysilane groups.
• Suitable oligomeric organoalkoxysiloxanes having aminoalkyl groups as crosslinker V are those that are commercially available for example under the trade names Dynasylan ® 1146 from Evonik Degussa GmbH or Hansa Care 8038 from CHT GmbH or Wacker ® Crosslinker ME 60 from Wacker Chemie AG.
• Crosslinkers V that are alkoxysilanes containing organic functional groups may have the additional advantage that they act as adhesion promoters and improve adhesion on various substrates.
• the functional group is, for example, an aminopropyl, glycidoxypropyl, (meth)acryloxalkyl, or mercaptopropyl group. Preference is given to amino-functional groups.
• the alkoxy groups of such silanes are usually a methoxy or ethoxy group.
• aminopropyltrimethoxysilane 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane and 3-mercaptopropyltriethoxysilane. It is also possible to use a mixture of adhesion promoters.
• adhesion promoters are, for example, also amino-functional alkylsilsesquioxanes such as amino-functional methylsilsesquioxane or amino-functional propylsilsesquioxane, alkoxylated alkyleneamines, especially ethoxylated and/or propoxylated alkylenediamines, and further, especially substituted, oligomers, polymers or copolymers based on polyalkylene glycols.
• amino-functional alkylsilsesquioxanes such as amino-functional methylsilsesquioxane or amino-functional propylsilsesquioxane
• alkoxylated alkyleneamines especially ethoxylated and/or propoxylated alkylenediamines
• substituted, oligomers, polymers or copolymers based on polyalkylene glycols especially substituted, oligomers, polymers or copolymers based on polyalkylene glycols.
• organoalkoxysilane or organoalkoxysiloxane crosslinker V used for the silicone composition of the invention may of course also be any mixture of the abovementioned silanes and/or siloxanes.
• Oxime groups include aldoxime groups and ketoxime groups.
• Such oxime groups are in the prior art usually present in the crosslinker of one-component moisture-curable silicone formulations when faster curing through the addition of water is desirable.
• the oxime compounds pose higher environmental hazards; also, the presence of such oxime groups means that oximes having an unpleasant odor are released during curing.
• the composition comprises between 0.5 wt.-% and 10 wt.-%, preferably between 1 wt.-% and 5 wt.-%, of said crosslinker V, based on the total composition.
• the composition comprises between 0.1 wt.-% and 5 wt.-%, preferably between 0.5 wt.-% and 3 wt.-% of aminofunctional such crosslinkers V, based on the total composition.
• composition of the invention optionally but preferably contains at least one non-reactive polydiorganosiloxane plasticizer PL.
• Such silicone plasticizers are known and widely used in the field. They normally consist of unreactive silicone oils, being polymers with the same polydiorganosiloxane, in particular polydimethylsiloxane, backbone but different end groups as polymer P.
• plasticizers PL offers the advantage of facilitated compounding of the composition, especially when fillers are used, and it may improve application properties and mechanical properties after curing.
• polydimethylsiloxane plasticizers PL that may optionally be used are trialkylsilyl-terminated polydimethylsiloxanes, the trialkylsilyl-terminated polydimethylsiloxanes preferably having a viscosity at 23°C in the range from 1 to 10'000 mPa.s.
• trimethylsilyl-terminated polydimethylsiloxanes in which some of the methyl groups have been replaced by other organic groups such as phenyl, vinyl or trifluoropropyl groups.
• the polydiorganosiloxane plasticizer PL may also be monofunctional, i.e. reactive at one end, for example via a hydroxy end group.
• Certain hydrocarbons may likewise be used as plasticizers or extenders, additional to or instead of polydiorganosiloxane plasticizers.
• the composition comprises between 5 wt.-% and 25 wt.-%, preferably between 10 wt.-% and 20 wt.-%, of said polydiorganosiloxane plasticizer PL, based on the total composition.
• composition of the invention further comprises between 0.01 wt.-% and 2.0 wt.-%, preferably between 0.1 wt.-% and 1 wt.-%, based on the total composition, of at least one radical scavenger RS , wherein said radical scavenger RS is selected from hindered amine light stabilizers that do not contain an N-H group in their molecular structure.
• Hindered amine light stabilizers are well known in the field of adhesives and sealants. However, they are hardly ever used in silicones, but rather in curable compositions based on chemically and physically more sensitive organic polymers such as polyurethanes, silane-functional organic polymers, or poly(meth)acrylates. Furthermore, they are used commonly in thermoplastic compositions such as polyolefins.
• HALS compounds are typically derivatives of tetramethylpiperidine (2,2,6,6-tetramethylpiperidine) and are primarily used to protect the polymers from the effects of photo-oxidation; as opposed to other forms of polymer degradation such as ozonolysis. They are also increasingly being used as thermal stabilizers for plastics, particularly for low and moderate level of heat, however during the high temperature processing of polymers (e.g. injection molding) they remain less effective than traditional phenolic antioxidants.
• HALS There are different types of HALS. Most common are so-called “basic HALS”, which contain a N-H group on their tetramethylpiperidine moiety. However, there are also so-called “non-basic HALS”, in which the N-H group has been converted to a N-R group, for example by acylation or by alkylation or by alkoxylation. HALS types that were alkoxylated are also called “NOR-HALS", as the N-H group was converted to a N-OR group.
• the radical scavenger RS must be selected from hindered amine light stabilizers that do not contain an N-H group in their molecular structure.
• Suitable radical scavengers RS are thus for example hindered amine light stabilizers that have at least one acylated, alkylated, or alkoxylated N-H group, and no remaining N-H groups.
• said radical scavenger RS contains at least one N-alkylated or N-acylated or N-alkoxylated 2,2,6,6-tetramethylpiperidine group, preferably an N-alkylated 2,2,6,6-tetramethylpiperidine group.
• radical scavenger RS having an acylated 2,2,6,6-tetramethylpiperidin group are, for example, Hostavin ® 3123 LIQ (Clariant) or Hostavin ® 3058 LIQ (Clariant).
• NOR-HALS ethoxylated 2,2,6,6-tetramethylpiperidin group
• BASF ethoxylated 2,2,6,6-tetramethylpiperidin group
• NOR-HALS ethoxylated 2,2,6,6-tetramethylpiperidin group
• An example of a suitable radical scavenger RS having an alkylated 2,2,6,6-tetramethylpiperidin group is, for example, Tinuvin ® 249 (BASF).
• the composition preferably comprises between 0.01 wt.-% and 2.0 wt.-%, in particular between 0.1 wt.-% and 1.5 wt.-%, preferably between 0.25 wt.-% and 1 wt.-%, based on the total composition, of said at least one radical scavenger RS .
• radical scavenger RS already low amounts lead to remarkable effects, while excessive amounts (for example more than 2 wt.-%) do not further improve the properties, but might lead to incompatibility with the silicone matrix.
• composition of the invention may optionally also comprise further constituents such as those customary in one-component moisture-curable silicone formulations.
• additives are fillers, OH-terminated polydimethylsiloxanes, plasticizers, extenders, adhesion promoters, curing accelerators, OH scavengers, drying agents, wetting aids, rheology modifiers, thixotropic agents, processing aids, biocides, UV stabilizers, heat stabilizers, flame retardants, color pigments, odorants, antistatic agents, and/or emulsifiers.
• the silicone formulation optionally includes one or more fillers.
• the fillers may influence, for example, both the rheological properties of the uncured formulation and the mechanical properties and surface characteristics of the cured formulation. It may be advantageous to use a mixture of different fillers.
• suitable fillers are inorganic or organic fillers, such as natural, ground or precipitated calcium carbonates or chalks, which are optionally surface-treated, for example with fatty acids, surface-treated silicas, in particular fumed silicas, aluminum hydroxides such as aluminum trihydroxide, carbon black, in particular industrial carbon blacks, barium sulfate, dolomite, silicas, kaolin, hollow beads, quartz, calcined aluminum oxides, aluminum silicates, magnesium aluminum silicates, zirconium silicates, cristobalite flour, diatomaceous earths, micas, titanium oxides, zirconium oxides, gypsum, graphite, carbon fibers, zeolites or glass fibers, the surface of which is optionally treated with a hydrophobizing agent.
• inorganic or organic fillers such as natural, ground or precipitated calcium carbonates or chalks, which are optionally surface-treated, for example with fatty acids, surface-treated silicas, in particular fumed silicas
• the composition according to the invention contains a silica, in particular a fumed (pyrogenic) silica, preferably a hydrophilic fumed silica.
• a (hydrophilic) silica is a solid that consists predominantly of Si(-O) 4 units but may also have surface silanol groups and has a three-dimensional, normally porous structure. The expression "hydrophilic” indicates that the silica has not been surface-treated with hydrophobizing additives.
• Hydrophobic silicas are surface-coated by hydrophobic agents, such as silanes having alkyl groups.
• Hydrophilic, i.e., untreated, silicas are well known as fillers and thickeners to the person skilled in the art. They can be produced, for example, via precipitation reactions (precipitated silica) or pyrolysis processes (fumed silica).
• Fumed silica is preferred for the invention, since it has a lower water content as a consequence of the production process and does not need to be dried. Precipitated silicas are, however, also suitable.
• silicas having a BET surface area from 50 to 300 m 2 /g, preferably from 100 to 255 m 2 /g.
• the composition preferably comprises between 1 wt.-% and 10 wt.-%, in particular between 2.5 wt.-% and 7.5 wt.-%, preferably between 3 wt.-% and 6 wt.-%, based on the total composition, of silica, in particular fumed silica, more preferably fumed hydrophilic silica.
• the composition according to the invention contains calcium carbonate (chalk) as filler, in particular a ground calcium carbonate.
• chalk calcium carbonate
• ground calcium carbonate in particular from natural resources (chalk, marble) is preferred.
• the calcium carbonate may be surface-coated, e.g., by stearates or silanes. Surface-coated calcium carbonate is often easier to compound within the composition.
• there are no specific limitations regarding the calcium carbonate filler there are no specific limitations regarding the calcium carbonate filler.
• the composition preferably comprises between 10 wt.-% and 50 wt.-%, in particular between 15 wt.-% and 40 wt.-%, preferably between 20 wt.-% and 30 wt.-%, based on the total composition, of calcium carbonate fillers.
• the total amount of fillers of any kind within the composition preferably is in the range of between 20 wt.-% and 60 wt.-%, preferably between 25 wt.-% and 50 wt.-%, based on the total composition, of fillers.
• composition of the invention may be mixed with one another in a customary manner, for example with the aid of a suitable mixing unit, such as a mechanical or planetary mixer.
• a suitable mixing unit such as a mechanical or planetary mixer.
• composition of the invention is preferably free of oxime compounds.
• the composition of the invention does not contain any chemical or physical drying agents.
• the composition in some preferred embodiments does not contain molecular sieves, calcium oxide, or vinyltrimethoxysilane.
• the invention further provides for a method for improving storage stability and pumpability of a one-component moisture-curable silicone composition, comprising the step of adding between 0.01 wt.-% and 2.0 wt.-%, preferably between 0.1 wt.-% and 1.0 wt.-%, based on the total composition, of at least one radical scavenger RS which is selected from hindered amine light stabilizers that do not contain an N-H group in their molecular structure, to a one-component moisture-curable silicone composition comprising
• composition of the invention may be used as an adhesive, coating or sealant in a method for bonding or joining substrates.
• the method of the invention comprises
• the composition of the invention is stored in an airtight container, for example a cartridge, a bag or a hobbock, and is thus storage stable.
• the silicone composition of the invention should be substantially free of water when stored in its container.
• the silicone composition of the invention preferably comprises less than 1.0% by weight of water, preferably less than 0.5% by weight of water, more preferably less than 0.1% by weight of water, based on the total composition.
• a low water content may in particular be achieved by pre-drying the constituents of the invention, in particular the fillers, if present. Heat and/or vacuum treatments have been found to be suitable therefor. These are known to the person skilled in the art of silicone formulation.
• the container is opened, and the composition then immediately applied to or introduced onto the substrate or into the bonded joint using a hand-held device, for example a gun, or using an automated application device.
• a hand-held device for example a gun
• an automated application device for example a hand-held device, for example a gun
• the composition of the present invention is especially suitable for automated application using pumps.
• step a) of the method mentioned above may be carried out in a customary manner, for example manually or in an automated process with the aid of robots.
• the substrate provided with the mixture is contacted with a further substrate, optionally under pressure, in order to obtain an adhesive bond between the substrates.
• the mixture is then left to cure in step b), usually at room temperature, in order to achieve the bonding or joining of the substrates.
• the bonded or joined substrates of the invention are obtained with the cured composition as adhesive or sealant material.
• the substrates to be bonded, coated, potted or joined may be of the same material or a different material. All customary materials may be bonded, coated, potted or joined with the one-component composition of the invention.
• Preferred materials for bonding, sealing, coating, potting or joining are glass, metals, such as aluminum, copper, steel or stainless steel, wood, wood substrates with paint treatment or other treatment, concrete, mortar, building stones such as sandstone and sand-lime brick, asphalt, bitumen, plastics, such as polyolefins, PVC, polyvinyl fluoride, PET, polyamide, polycarbonate, polystyrene or polyacrylate, and composite materials such as CFRP.
• the one-component composition of the invention may thus be used as an adhesive, sealing, coating, potting compound or sealant, for example in the following sectors: construction, the sanitary sector, the automotive sector, solar power, wind power, white goods, facade and window construction, electronics, and boat- and shipbuilding.
• Table 1 Chemicals used. Name Description Polymer P Alkoxysilane-terminated, crosslinkable PDMS polymer having a viscosity of 80 Pa ⁇ s at 23°C (Wacker ® Polymer AL 100; Wacker Chemie) (polydiorganosiloxane P ) Plasticizer PL ⁇ , ⁇ -Bis(trimethylsilyl)-poly(dimethylsiloxane) having a viscosity of 1'000 mPa ⁇ s at 23°C (Wacker ® Plasticizer 1000; Wacker Chemie) (polydiorganosiloxane plasticizer PL ) Crosslinker V1 Mixture of alkoxysilane with aminofunctional siloxane (Wacker ® Crosslinker ME 60; Wacker Chemie) (crosslinker V ) Crosslinker V2 N-2-Aminoethyl-3-aminopropyltrimethoxysilane (
• table 4 contains the summaries of the measurement results. All tests were carried out at 23°C and 50% RH (relative humidity).
• Viscosity was determined at 25°C in accordance with DIN EN ISO 3219 using a MCR301 Rheometer from Anton Paar, Austria, with a type PP 25 spindle and a distance of 1 mm. The reported viscosity values relate to a shear rate of 0.89 s -1 .
• a first viscosity measurement was taken on freshly prepared samples stored for 24h at 23°C and 50% RH in closed cartridges.
• a second measurement was taken on samples that were stored for 1 week in closed cartridges in an oven at 70°C, before being stored again for 24h at 23°C and 50% RH. This second measurement was done to investigate the storage stability under thermal ageing conditions. Furthermore, the percentual increase in viscosity between the fresh sample and the thermally aged sample was determined. The larger the increase in viscosity between the two samples, the poorer the storage stability.
• extrusion rate The pumpability properties (extrusion rate ) were determined according to ASTM D-5267 on freshly prepared samples stored for 24h at 23°C and 50% RH in closed cartridges. The indicated value (in g/min) is an average taken over 3 measurements. The higher the extrusion rate, the better the pumpability of the composition. Table 3: Example compositions. All numbers in wt.-%.
• Table 4 shows that inventive example Z-4 shows a significantly lower increase in viscosity after thermal ageing, alongside with a significantly higher extrusion rate than both the reference example containing no additive (Z-1) and the reference examples containing additives not according to the invention (Z-2, Z-3, Z-5). This is very surprising, especially given the fact that some of the comparative additives are structurally very similar to the additive of Z-4 (see table 2).

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